Machines for polishing or lightly grinding elongated workpieces



July 16, 1957 B. v. DAVIS MACHINES FOR POLISHING OR LIGHTLY GRINDING ELONGATED WORKPIEICES Filed Nov 21, 1955 5 Sheets-Sheet 1 B. V. DAVIS MACHINES FOR POLISHING OR LIGHTLY GRINDING July 16, 1957 ELONGATED WORKPIECES 5 Sheets-Sheet 2 Filed Nov. 21, 1955 Pica.

y 5 B. v. DAVIS 2,799,126

MACHINES FOR POLISHING OR LIGHTLY GRINDING ELONGATED WORKPIECES 'Filed Nov. 21, 1955 5 Sheets-Sheet 5 July 16, 1957 B v DAVIS 2,799,126

MACHINES FOR POL. ISH ING OR LIGHTLY GRINDING' ELONGATED WORKPIECES Filed Nov. 21, 1955 5 Sheets-Sheet 4 O 7 I l I U'I I so 2| m 4;

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MACHINES FOR POLISHING OR LIGHTLY GRINDING ELONGATED WORKPIECES Filed Nov 21' Inv or United States Par m- MACHINES FOR POLISHING R LIGHTLY GRINDDNG ELONGATED WORKPIECES Bernard V. Davis, Coventry, England, assignor to Arm- Claims priority, application Great Britain December 7, 1954 6 Claims. (Cl. 51-143) This invention relates to a machine for polishing, or lightly grinding, an elongated work-piece having a curved surface, for example, a compressor blade.

Polishing such work-pieces by hand is a long and tedious job particularly when the surface of the workpiece follows a complicated curve, an excellent example of which is the aerofoil surface of a compressor blade.

An object of the invention is to provide a machine which will accurately polish, or lightly grind, one side (at a time) of such a work-piece in accordance with a predetermined contour set up on a former.

According to the invention, the machine comprises a base carrying a vertically-slidable member having two arms, one of the arms carrying a part-spherical rotatable follower roller, and the other arm carrying a rotatablydriven polishing head, the arm carrying the follower roller being vertically-movable relatively to the vertically-slidable member to a limited extent to a predetermined position, the head and roller being spaced on opposite sides of the vertical axis of the slidable member, and the machine including a former-carrying table and a work-piececarrying table, the tables being automatically reciprocable together relatively to the head and follower both longitudinally and transversely of the base, whereby the said curved surface of the work-piece is polished, or ground, in accordance with the contour of the former.

V Preferably the work-piece-carrying table supports an oil bath in which the work-piece is immersed and into which the polishing head dips whereby the polishing takes place entirely in the oil, the oil also serving to maintain the work-piece cool. 7

Anotheroptional, but preferable, feature of the invention is that the slidable member is supported in a relatively wide and long channel to minimise errors in the relative positions of the follower roller and polishing head resulting from any deflection due to sliding clearances between the slidable member and channel.

The polishing head can be in the form of a pulley wheel having a convex outer surface over which passes a polishing band having an abrasive surface, such as emery. The band can be maintained lightly in tension by a spring-loaded jockey pulley carried by the slidable member, and can be driven by any suitable means such as an electric motor also carried by the slidable member. It is preferable that the downward force exerted on the slidable member by the weight of the motor and part of. the weight of the slidable member are counter-balanced, for example, by a weight carried by a cable connected to the slidable member.

.'. In the accompanying drawings:

Figure -1 is a plan of a machine, for polishing gas turbine blades, according to the invention;

Figure 2 is an enlarged section on line 22 of Figure 1;

Figure 2a is an enlarged section of the pawl and pinion arrangement of Figure 2;

Figure 3 is a section on line 3-3 of Figure 1;

Figure 4 is a section on line 44 of Figure 3, a portion of the machine (on the right-hand side) being omitted;

Figure 5 is an enlarged section on line 5--5 of Figure 4 of a polishing head which is also shown, to a smaller scale, in Figures 1 and 3;

. Figure 6 is an end elevation of the upper part of the machine, the cover and oil bath of the machine, only, being shown in section;

Figure 7 is a schematic diagram of the main portion of the control circuit of the machine;

Figure 8 is an enlarged plan of a portion of the machine which is concealed by a cover in Figure 1;

Figure 9 is a schematic diagram of another portion of the control circuit for the machine; and

Figure 10 is a section through a manually-controllable restrictor.

The machinecomprises a rectangular base 10 supported by a pedestal 11, the base 10 having a longitudinal rectangular slot 12 (Figure 1) adjacent its mid-part, fast in'wh-ich is a vertical channel-section member 13 in which is carried the vertically-slidable member 14. The channel is relatively long and wide to minimise errors resulting from any deflection due to sliding clearances between the vertically-slidable member and the sides of the channel.

The member 14 is bolted to a slide 15 vertically slidable in guides 16 at its outer edges (Figure 3).

At its upper end the vertically-slidable member 14 carries two arms 17, 18 (Figures 1 and 4), one arm 18 supporting at its outer end a rotatable polishing head 19, and the other arm 17 supporting at its outer end a rotatable part-spherical follower roller 20. The follower roller 20 and polishing head 19 are equally spaced from, and on opposite sides of, the vertical axis of the vertically-slidable member 14.

The arm 18 carrying the polishing head 19 is integral with the vertically-slidable member 14; and the polishing head 19 is open at one side (see Figures 1 and 5) to enable the head 19 to polish close to a platform of the blade 21.

a The arm 17 carrying the follower roller 20 is supported in a dovetail slide 22 on the slidable member 14 and is vertically-slidable by a manually-controllable screw 23 and nut 24 device (see Figure 4) so that the position of the follower roller 2 0 can be pre-adjusted by minute amounts relatively to the slidable member 14.

The follower roller 20 is rotatably supported in a transverse bearing 25 (Figure 4) and the polishing head 19 is rotatably supported in a longitudinal bearing (see Figure 5).

The construction of the polishing head 19 is seen in detail in Figure 5. The arm 18 carries a bolt 26 on to which a polishing head pulley, or roller, 27 is rotatably mounted by means of a double row combined journal and thrust bearing 28.

Bonded to the pulley 27 is a layer of rubber 30 of partspherical external contour 31, A polishing band 32 having an emery coating 33 passes round the polishing head pulley 27;

The radius of the part-spherical contour 31 of the 3 polishing head pulley 27 is such that with the addition of the thickness of the polishing band 32 and emery coating 33 an eifective part-spherical operative surface will be provided which is exactly similar to that of the follower roller 20.

The vertically-slidable member carries a pair of pulleys 34, 35 (Figures 3, 4 and 6) mounted one above the other and the polishing band 32 passes over the two pulleys 34, 35, the polishing head roller 27, and a-driving pulley 36 driven by an electric motor 37 carried by the vertical slide 15 below the base 10. A spring-pressed jockey pulley 38 carried by an arm.39 pivoted on the slide-15 (Figure 4) acts upon the polishing band 32 to maintain it lightly in tension. The tension is adjustable by a-knob 40 threaded on a pivoted rod 41, a spring 42 being interposed between the knob 40 and the arm 39.

The weight of the electric motor 37 and the majorpart of the weight of the vertically-slidable member =14, slide 15 and other parts carried thereby are counter-balanced by weights 43 (Figures 3 and 4) attached to aacable 44 which passes over a system of pulleys 45 and is connected to the slide 15 at 46. Thus only the remaining small downwardly-acting part of the total slidable weight is used for maintaining the follower roller 20 in contact with the former 47.

The former 47 is mounted on a fixture 47a supported on a rectangular former-carrying table 49 and located thereon in both directions by means of coacting tenon and slot connections indicated at 48, the table being'supported so as to be slidable longitudinally by means of a V-rail 50 engaged in a V-groove 51 in a table carrier 52. The latter extends across the machine and supports beneath the polishing head a work-piece-carrying table 54, in this instance adapted to support a fixture 21a carrying a gas-turbine compressor blade 21, the fixture being located in both directions by coacting tenon and slot connections similar to those for the table 49' and indicated at 55.

The tenon and slot connections for locating the workpiece and former are arranged so that the former and work-piece can only be clamped on their respective tables in one position; but the work-piece can be rapidly removed and replaced by another work-piece.

The table 54 is also longitudinally slidable relatively to the machine by coacting flat horizontal slide surfaces 56, 57 on the table 54 and carrier 52, respectively. The two tables 49, 54 are integrally connected together at their ends at 53 so as to be longitudinally-reciprocable in unison.

The table carrier 52 is also transversely movable relatively to the machine and is supported (Figure 3) by means of a V-rail 58 and fiat sliding surface 59 engaging co-operating surfaces on the base 10.

The work-piece-carrying table 54 supports a surrounding oil bath 60 into which the polishing head 19 projects. The oil level (indicated by a dotted line) in the bath 60 is such as to immerse the blade 21 completely. The use of an oil bath ensures that all dust produced is retained in the oil and settles to the bottom of the bath.

A hinged cover 61 for the machine is provided to enclose the working parts, such as the grinding wheel 19 and follower 20, at the head of the machine; and the cover 61 is carried by a hinge 61a. The hinge 61a is supported by a web 6117 from the table 54 as shown in Figures 3, 4 and 6.

The operation of the machine is described fully hereinafter with reference to Figures 7 and 9 but, briefly, the two tables 49, 54 are movable together longitudinally of the machine by pneumatic-hydraulic pressure, the ma chine carrying automatic trips so that the direction of movement is reversed at each end of the polishing stroke. Transverse movement of the two tables 49, 54 is initiated by a stop on one table actuating a trip during each longitudinal movement of the tables so as to feed the table carrier 52 in steps transversely of the machine (say, six-thousandths or twelve-thousandths of an inch per step), the transverse movement taking place when the blade is approximately at the centre of its longitudinal travel.

The operation of the machine is as follows:

(These operations are performed by the components of the machine shown in diagrammatic detail in Figure 7.)

The longitudinal movements of the tables 49, 54 are caused by a double-acting hydraulic piston and cylinder arrangement 62, 62a (Figures 4 and 7), the oil supply to which is controlled by air-operated dash-pots 63 and 64 (Figures 6, 7 and 8).

The piston 62a is provided with abobbi'n'95 (Figures 2 and 6) which engages a downwardly depending forked plate 96 fast with the table 49 whereby movement of the piston 6211 causes corresponding reciprocating movement of the table 49.

The transverse movements of the tables 49, 54 are caused by a single acting, pneumatic piston and cylinder arrangement 65, 65a which has a return spring 65b (Figures 2 and 7 The piston 65a-acts through a pawl 67 and pinion 66.

The piston 65a is limited in its movements by a variable stop 97. The stop 97 has four positions in whichtour diflferent stop surfaces 98, 99, and 101 are brought opposite the end of the piston. The stop 97 is movable to any one of these four positions by a knob 102a (Figure 1).

On movement of the piston 65a the spring-pressed pawl 67 engages and turns the pinion 66 an amount dependent on the setting of the stop 97. The pinion 66 is fast with a lead-screw 102 (Figure 4) threaded in a bore in a block 103 fixed to the base 10 of the machine, so that rotation of pinion 66 causes rotation of lead-screw 102 which in turn causes transverse movement of the tables 49, 54.

The main inlet port 68 (Figure 7) is connected to a source of compressed air, and air from port '68 passes through regulator 69 (Figures 6, 7 and 8) and to a-threeport manually operable valve 70 (Figures 1, 4 and 7) which is the on-otf valve for longitudinal reciprocation of tables 49, 54.

When the switch 70 is on the air passes through the valve 73 (Figures 6 and 7), operable by means of an arm 73b carrying a roller 730 to allow air to flow to a five-port valve 74 (Figures 7 and 8) and also to allow air to flow to roller-operated three-port valves 75 and 76. The air passes through the five-port valve 74 to one or other of the dash-pots 63, 64 according to which of two roller-operated three-port valves 75, 76 is open. A dash-pot is defined as a cylinder having a restriction at one end and containing a floating. piston. The dashpots are arranged to clamp movements of the piston 62a in the cylinder 62.

The dash-pots 63, 64 are air-operated to force oil into the cylinder of the piston and cylinder arrangement 62 and the valve 74 controls the flow of air into one of the dash-pots, e. g., 64, and out of the other dashpot, e. g., 63. Oil flows from the appropriate dash-pot to one end of the piston and cylinder arrangement 62 through one or other of two manually-controllable restrictors 77 (Figures 6, 7 and 8 and 10). The restrictor 77, which is shown schematically in Figure 7 and diagrammatically in Figure 6, is shown in section in Figure 10. For restricted flow fluid enters the 'restricto'r 77 at and flows past conical restrictor headrll2, the position of which is governedby the knob 113, and out through passage 111. Flow in the opposite direction is unrestricted because the fluid pressure entering passage 114 raises the ball 115 against pressure of the spring 116 and the fluid flows past the ball and out throughpassage 110. At the end of the piston stroke one or other of the valves 75, 76 is opened which causes a piston in valve 74 tomove so as to allow free passage :of air to the opposite dash-pot .(63 or '64) and to exhaust the other dash-pot (64 or 63 respectively).

The roller-operated valve 73 is closed by the adjustable stop 73a at a predetermined position at the completion of the cycle of operation.

The air also passes through roller-operated valve 71 (Figures 6 and 7) which is depressed on every longitudinal reciprocation of the tables 49, 54 to allow air to pass through a manual on-oif switch 72 (Figures 1 and 7) to the pneumatic piston and cylinder arrangement 65 to cause traverse of the table in steps.

Thus it will be appreciated that at the centre of every table stroke, i. e., at the centre of every stroke of the piston of piston and cylinder arrangement 62, a stop 71a on table 49 (Figures 4 and 6). operates valve 71 and allows impulses of air to pass through manual on-olf switch 72 to the pneumatic piston and cylinder arrangement 65 to cause the cross-indexing movement to take place.

The head is lifted and lowered by manual control at the beginning and end of a polishing operation by means of the circuit shown in Figure 9. The main compressed air supply comes in at 78 and the air flows through a filter 79 and a lubricator 80 to the point 68 which provides the air supply for the units shown in Figure 7. The air also flows to a five-port valve 81 which has a manual control lever 82. One outlet 83 of the five-port valve 81 is connected to a variable one-way flow restrictor 84 to one end of a piston and cylinder arrangement 85 the piston 86 of which is connected to the vertical slide 15 supporting the vertically-slidable member 14 (Figure 3).

Another port 87 of the valve 81 is connected to the other end 88 of the piston and cylinder arrangement 85. Two ports 89 and 90 go to exhaust. When it is desired to raise the member 14 the manual lever 82 is moved to the position shown in dotted line so that the air supply passes through the flow restrictor 84, which in this direction of flow provides free flow, and thence to the lower end of the piston and cylinder arrangement 85 to raise the piston 86 rapidly and thereby to raise the vertical slide 15 and vertically-slidable member 14 rapidly. Air exhausts from the upper end 88 of the piston and cylinder arrangement 85 through the exhaust port 90.

To lower the member 14 the manual lever 82 is moved to the position shown in solid line and the opposite sequence of events take place, the flow restrictor 84 acting to restrict exhaust of air from the piston and cylinder arrangement 85 so that the member 14 is lowered slowly to bring the follower roller 20 into contact with the former 47. The speed with which the downward moverneut takes place can be controlled by means of the variable one-way restrictor 84.

In operation a fixture with former 47 is set up on the former-carrying table 49 and clamped in position; and the arm 17 carrying the follower roller 20 is adjusted so as to determine the depth of cut required of the polishing head 19 when the roller 20 is in a position in contact with the former 47. With the tables 49 and 54 in the extreme forward position the work-piece (blade) 21 is set up in the table 54 and clamped in .position. The motor 37 is then started so as to start the abrasive band 32 moving. The work-piece 21 is moved longitudinally backwards and forwards with intermediate transverse steps (as described with reference to Figure 7) below the rotating polishing head 19 so that the abrasive surface of the band 32 contacts and polishes the work-piece 21 in accordance with the contour of the former 47.

A manually-operable handwheel 91 (Figures 1, 4 and 6) is fact with the lead-screw 102 and rotates with it during machine operation. The handwheel 91 can be used for manual adjustrnents of the tables 49 and 54 transversely of the machine for setting-up purposes.

A manually-engageable and operable handwheel 92 (Figures 1 and 6) is arranged to drive a pinion 164 cugaged with a rack 105 for manual longitudinal movements of the tables 49 and 54.

The hydraulic pressure can be varied, by means of the restrictors 77, 'so'that the longitudinal movement of the work-piece-carrying table 49 and the former-carrying table 54 can be varied from zero to 5" in 4 seconds.

What I claim as my invention and desire to secure by Letters Patent of the United States is: a

1. A machine for polishing, or lightly grinding, an elongated work-piece having a curved surface, the machine comprising a base, a vertically-slidable member having two arms, the member being slidably supported by the base, a part-spherical rotatable follower roller carried by one of the arms, and a rotatably-driven polishing head carried by the other of the arms, the arm carrying the follower roller being vertically-movable relatively to the vertically-slidable member to a limited extent to a predetermined position, the head and roller being spaced on opposite sides of the vertical axis of the slidable member, and the machine including a formercarrying table and a work-piece-carrying table, the machine comprising means for automatic reciprocation of the tables together relatively to the head and follower longitudinally of the base, and for automatic transverse movement in steps in one direction only, of the tables together relatively to the head and follower whereby the said curved surface of the work-piece is polished, or ground, in accordance with the contour of the former.

2. A machine according to claim 1 and including an oil bath supported by the work-piece-carrying table, the work-piece being immersed in the oil bath and the polish ing head dipping into the oil bath, whereby the polishing takes place entirely in the oil.

3. A machine according to claim 1 and in which the slidable member is supported in a relatively wide and long channel to minimize errors in the relative positions of the follower roller and polishing head resulting from any deflection due to sliding clearances between the slidable member and channel.

4. A machine for polishing, or lightly grinding an elongated work-piece having a curved surface, the machine comprising a base, a vertically-slidable member having two arms, the member being slidably supported by the base, a part-spherical rotatable follower roller carried by one of the arms, and a rotatably-driven polishing head carried by the other of the arms, the arm carrying the follower roller being vertically-movable relatively to the vertically-slidable member to a limited extent to a predetermined position, the head and roller being spaced on opposite sides of the vertical axis of the slidable member, and the machine including a former-carrying table and a work-piece-carrying table, the machine comprising means for automatic reciprocation of the tables together relatively to the head and follower longitudinally of the base, and for automatic transverse movement in steps in one direction only, of the tables together relatively to the head and follower whereby the said curved surface of the work-piece is polished, or ground, in accordance with the contour of the former, the polishing head being in the form of a pulley wheel having a convex outer surface over which passes a polishing band having an abrasive surface, such as emery.

5. A machine according to claim 4 and including a spring-loaded jockey pulley by which the band is maintained lightly in tension.

6. A machine for polishing, or lightly grinding, an elongated work-piece having a curved surface, the machine comprising a base, a vertically-slidable member having two arms, the member being slidably supported by the base, a part-spherical rotatable follower roller carried by one of the arms, and a rotatably-driven polishing head carried by the other of the arms, the arm carrying the follower roller being vertically-movable relatively to the vertically-slidable member to a limited extent to a predetermined position, the head and roller being spaced on opposite sides of the vertical axis of the slidable memher, and the machine including a former-carrying table r and-:2 wafk piace carrying table, the-machine com risin ni'e'afis ftiratitch1at'i reciprocation bf the tables together 'ielativly tp the head and fdllower longitudinally of the base, fafil "farautomatic fiansve'rse movement in steps in one'dire'ctionhfily; ofthe tHBl'es together ielatively to the head and fQllqwqrjvhreby the"sa'id curved surface of the workpiece is \p61i's1hd,"0r ground, -in accordance with 'the contour of the "fofirii, the machine including a motor carrid by t11"$1id151'fiimbet and driving the olishing head, Ifieansfbeing provided whereby the 'd'ownwar'd'fo'rce exerted on the slidable member. by 'the weight of th'e motor and part of the weight of 'th'e'sli'dable memb'ris couhter balan'ced.

ReferencesCitedin the'file of this patent UNITED'STAT-ES PATENTS 

